One's cheek weld force on the butt stock determines how much pressure there is on the stock. That effects how much the bore axis moves off its direction to the target when the primer fired and the bullet's going down the barrel. Different cheek weld pressures means the rifle's movement during the bullet's barrel time will be different. While the inheirent accuracy of the rifle and ammo are still intact, it centers at different places on the target with different amounts of pressure on the stock from us humans.

So does putting the butt pad at different places in ones shoulder from shot to shot. As does different sling tension.

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US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master